package 乙级;

import java.util.Scanner;

/**
 * @author mubei
 * @date 2021/8/20
 * @description
 */
public class 程序计算时间 {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        int start = scanner.nextInt();
        int end = scanner.nextInt();

        int d = (end - start)/100;
        if((end-start)%100>=50){
            d+=1;
        }
        int h = d/60/60;
        String sh = two(h+"");
        int m = d%(60*60)/60;
        String sm = two(m+"");
        int s = d%60;
        String ss = two(s+"");

        System.out.println(sh +":"+ sm+":"+ss);
    }

    public static String two(String s){
        if(s.length()<2){
            s = "0"+s;
        }
        return s;
    }

}
